Abstract: Methods and systems for restricting the launch of virtual application files. In one embodiment, a launching application is signed with a digital signature. When the launching application launches a runtime engine and instructs it to execute an application file, the runtime engine determines whether an entity identifier associated with the launching application identifies an authorized entity. If the entity identifier identifies an authorized entity and the digital signature is valid, the runtime engine executes the application file. In another embodiment, a ticket is transmitted to the launching application along with an instruction to launch the application file. The ticket includes a digital signature and an expiration date. The launching application communicates the ticket to the runtime engine, which will execute the application file only if the digital signature is valid and a current date is not later than the expiration date.